Optical Device Alignment Methods

The present invention relates to methods and devices for aligning optical devices and systems.

During manufacture and assembly of image projecting optical devices, and more specifically, micro-display projectors, it is necessary to align and focus optical components of, and relating to, the optical device to achieve best performance. An example of a micro-display projector is disclosed in U.S. Pat. No. 7,643,214 to Lumus Ltd., wherein a display source and collimating optics are assembled into the micro-display projector. Light waves corresponding to the image to be projected are coupled into a light-guide optical element (LOE) by the micro-display projector that can be placed at the edge of the LOE, and can be configured in eyeglasses, such as embedded in the temple of the eyeglasses, or attached to a head-mounted display apparatus. The coupled-in light waves are guided through the LOE, by total internal reflection, and are coupled-out of the LOE as image light waves by one or more partially reflecting surfaces and into an eye (or eyes) of a user (i.e., viewer).

In conventional focusing and alignment methods, the various optical components of the micro-display projector are moved, relative to each other, via displacement and translations. However, such displacement and translations often result in the display source falling out of alignment with other major components of the micro-display projector, resulting in degradation in illumination uniformity. In addition, conventional focusing and alignment procedures typically rely on an image sensor (i.e., camera) capturing an image corresponding to light waves projected by the micro-display projector. Using the example of the LOE and the micro-display projector disclosed in U.S. Pat. No. 7,643,214, a conventional focusing and alignment procedure would require independently moving the display source of the micro-display projector to focus and align the components of the micro-display projector, coupling light waves from the micro-display projector into the LOE, and capturing the light waves coupled-out of the LOE as an image. However, misalignment of the image sensor and the micro-display projector can lead to misalignment of the components of the micro-display projector. Specifically, if the image sensor is rotated about a principle axis (e.g., optical axis), then the display source will ultimately be incorrectly aligned with other components of the micro-display projector. This is a particular problem when using two optical systems (i.e., two micro-display projectors and two LOEs) with one optical system deployed for each eye of a user, for example, as used in a stereo vision system. If the micro-display projector of each optical system is not properly aligned, each display source will provide an image at a different rotation angle, resulting in an incorrect stereo image.

The present invention is directed to methods for performing alignment of optical devices and systems.

According to the teachings of an embodiment of the present invention, there is provided a method for aligning and focusing components of an optical device. The method comprises: displacing a display source along a displacement axis to adjust a distance between the display source and a collimating prism assembly, the display source and an illumination module being aligned with an illumination prism assembly such that light waves emitted by the illumination module arrive at the display source via the illumination prism assembly; and translationally moving, in unison, the display source, the illumination prism assembly, and the illumination module in a plane normal to the displacement axis.

Optionally, the translationally moving includes moving the display source, the illumination prism assembly, and the illumination module together as a single unit.

Optionally, the displacing includes moving the display source, the illumination prism assembly, and the illumination module together as a single unit so as to adjust the size of a gap between the illumination prism assembly and the collimating prism assembly.

Optionally, the display source and the illumination prism assembly are aligned so as to produce a gap between the display source and the illumination prism assembly.

Optionally, the displacing includes moving the display source so as to adjust the size of the gap between the display source and the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling the display source to the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling the illumination module to the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling the display source to the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling the collimating prism assembly to the illumination prism assembly.

Optionally, the display source and the illumination module are aligned with the illumination prism assembly such that the display source is positioned along a first component of an optical axis of the illumination prism assembly, and the illumination module is positioned along a second component of the optical axis of the illumination prism assembly that is orthogonal to the first axis.

Optionally, the display source and the illumination module are mechanically coupled to orthogonal surfaces of the illumination prism assembly.

Optionally, the collimating prism assembly and the illumination module are mechanically coupled to orthogonal surfaces of the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling at least one of the display source, the illumination module and the collimating prism assembly to the illumination prism assembly.

Optionally, the mechanically coupling includes cementing one or more slabs of glass between the collimating prism assembly and the illumination prism assembly.

Optionally, the components of the optical device include the electronic display source, the illumination module, the illumination prism assembly, and the collimating prism assembly, and the mechanically coupling including deploying a gel between at least two of the components of the optical device.

Optionally, the method further comprises: mechanically coupling the illumination prism assembly and the illumination module to a mechanical assembly at a known orientation, the mechanical assembly including a test pattern at a known orientation; capturing an image of the test pattern when the image sensor is positioned at a first location in which the image sensor is aligned with the test pattern; analyzing the captured image to determine an estimated orientation of the test pattern; adjusting an orientation parameter of the image sensor based on a comparison between the known orientation of the test pattern and the estimated orientation of the test pattern; and capturing an image projected by the optical device when the image sensor is positioned at a second location in which the image sensor is aligned with the optical device.

There is also provided according to an embodiment of the teachings of the present invention a method for aligning components of an optical device. The method comprises: displacing a display source, an illumination module, and an illumination assembly, along a displacement axis so as to adjust the size of a gap between the illumination prism assembly and a collimating prism assembly, the display source and the illumination module being aligned with the illumination prism assembly such that light waves emitted by the illumination module arrive at the display source via the illumination prism assembly; and translationally moving, in unison, the display source, the illumination prism assembly, and the illumination module in a plane normal to the displacement axis.

There is also provided according to an embodiment of the teachings of the present invention a method for aligning an image sensor with an optical device. The method comprises: mechanically coupling at least one component of the optical device to a mechanical assembly at a known orientation, the mechanical assembly having a test pattern at a known orientation; capturing an image of the test pattern when the image sensor is positioned at a first location in which the image sensor is aligned with the test pattern; analyzing the captured image to determine an estimated orientation of the test pattern; and adjusting an orientation parameter of the image sensor based on a comparison between the known orientation of the test pattern and the estimated orientation of the test pattern.

Optionally, the method further comprises: capturing an image projected by the optical device when the image sensor is positioned at a second location in which the image sensor is aligned with the optical device.

Optionally, the optical device includes an image projecting device and a light waves-transmitting substrate, the method further comprising: coupling light waves, corresponding to an image projected by the image projecting device, into the light waves-transmitting substrate; coupling the coupled-in light waves out of the substrate as image light waves; and capturing the image light waves with the image sensor when the image sensor is positioned at a second location in which the image sensor is aligned with the light waves-transmitting substrate.

Optionally, the orientation parameter of the image sensor includes an angle of rotation about a principle axis of the image sensor.

Optionally, the test pattern is vertically oriented relative to a reference axis.

Optionally, the test pattern is horizontally oriented relative to a reference axis.

Optionally, the test pattern is oriented at an oblique angle relative to a reference axis.

Optionally, the orientation of the test pattern is defined by at least one orientation parameter, and the at least one orientation parameter of the test pattern includes an angular position of the test pattern relative to a reference axis.

Optionally, the test pattern is formed as an aperture in the mechanical assembly.

Optionally, the method further comprises: illuminating the test pattern.

Optionally, the method further comprises: moving the image sensor to the first location prior to capturing the image of the test pattern; and moving the image sensor to the second location after capturing the image of the test pattern.

Optionally, the optical device includes at least a display source, an illumination module, an illumination prism assembly, and a collimating prism assembly.

Optionally, the method further comprises: aligning the illumination module and the display source with the illumination prism assembly such that light waves emitted by the illumination module arrive at the display source via the illumination prism assembly; displacing the display source along a displacement axis to adjust a distance between the display source and the collimating prism assembly; and translationally moving, in unison, the display source, the illumination prism assembly, and the illumination module in a plane normal to the displacement axis.

Unless otherwise defined herein, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein may be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

The present invention is directed to methods for performing alignment of optical devices and systems.

The principles and operation of the methods according to present invention may be better understood with reference to the drawings accompanying the description.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Initially, throughout this document, references are made to directions such as, for example, upper and lower, top and bottom, left and right, and the like. These directional references are exemplary only to illustrate the invention and embodiments thereof.

1 FIG. 10 70 80 90 100 1 1 Referring now to the drawings,illustrates a schematic representation of a top view of an image projecting optical device, an LOE, an alignment module, an image sensor, and a display monitor, deployed in an example environmentin which embodiments of the present disclosure may be performed. The environmentmay be, for example, an optical laboratory test bench with various types of optical, mechanical, and electronic testing equipment.

1 60 10 70 60 70 70 70 80 60 66 90 60 66 90 80 70 66 60 90 66 The environmentincludes a mechanical assembly, to which the image projecting optical deviceis mechanically attached together with the LOE. The mechanical assemblyincludes one or more attachment mechanisms which hold the LOEat a fixed and known orientation. The LOEis deployed at the fixed and known orientation using calibrated optical test equipment, to ensure proper deployment of the LOE. The alignment moduleis also attached to the mechanical assemblyin a fixed and known orientation. A sliding arrangementattaches the image sensor (i.e., camera)to the mechanical assembly. The sliding arrangementenables the image sensorto slide between the alignment moduleand the LOE. A first portion (i.e., base portion) of the sliding arrangementslides along a railing deployed on a main portion of the mechanical assembly. The image sensoris mechanically attached to the sliding arrangementat a second portion (i.e., distal portion from the base portion) via a mechanical sub-assembly. The mechanical sub-assembly may be implemented as, for example, a platform having one or more joints allowing for rotational three degrees of freedom.

100 90 102 102 90 100 100 90 1 100 90 90 60 The display monitor, implemented, for example, as a liquid crystal display (LCD) or the like, is connected to the image sensorvia an interface connection. The interface connectioncan be implemented, for example, as a cable connected to respective input/output ports of the image sensorand the display monitor. The display monitoris operative to display images captured by the image sensorfor viewing by a user or operator of the environment. The display monitormay function as a viewfinder for the image sensor, allowing the user or operator to see changes in images captured by the image sensorin response to user initiated mechanical adjustments made to various components of the mechanical assembly.

60 60 61 63 65 61 10 10 60 63 70 70 60 61 63 10 70 10 70 65 80 80 60 The mechanical assemblymay include one or more sub-assemblies, each configured for holding different optical and/or mechanical components. In certain embodiments, the mechanical assemblyincludes at least three major sub-assemblies, namely a first sub-assembly, a second sub-assembly, and a third sub-assembly. The first sub-assemblyholds components of the image projecting optical deviceand attaches the components of the image projecting optical deviceto the mechanical assembly. The second sub-assemblyholds the LOEand attaches the LOEto the mechanical assembly. The sub-assemblies,are arranged to allow cooperative positioning of the image projecting optical deviceand the LOE, such that the light waves produced by the image projecting optical deviceare coupled in to the LOE. The third sub-assemblyholds the alignment moduleand attaches the alignment moduleto the mechanical assembly.

61 63 65 61 12 14 16 63 70 18 60 61 63 65 10 70 80 61 63 65 61 The sub-assemblies,,may be implemented in various ways, including, but not limited to, bracket arrangements, gripping arrangements, and pin/screw arrangements. In certain embodiments, the first sub-assemblycan be arranged to hold the electronic display source, the illumination module, and the illumination prism assembly, while the second sub-assemblymay be arranged to hold the LOEand the collimating prism assembly. The mechanical assembly, and the corresponding sub-assemblies,,, are arranged to maintain the alignment and orientation of the components of the image projecting optical device, the LOE, and alignment module, respectively. It is noted that the sub-assemblies,,, in particular the first sub-assembly, may include one or more sub-components to allow for controlled adjustment of the positioning of the components which are held by the sub-assembly. Such controlled adjustment will be described in detail in subsequent sections of the present disclosure.

10 10 70 10 90 70 90 70 70 70 70 90 70 10 70 90 100 70 10 10 70 Generally speaking, the embodiments of the present disclosure are directed to a two-stage alignment (i.e., calibration) process. In one of the stages, referred to as a focusing and alignment stage, the individual components of the image projecting optical deviceare focused and aligned such that the image projecting optical deviceproduces a sharp and focused image at the LOEoutput. The focusing and alignment is performed by moving sub-components of the image projecting optical devicewhile evaluating image quality metrics of images captured by the image sensorat the LOEoutput until certain performance criteria are met. Prior to performing the steps of the focusing and alignment stage, the image sensoris focused to infinity and positioned across from the LOE(i.e., aligned with the LOE) at an eye relief distance from the LOE(for example 18 millimeters), and preferably within an eye motion box, to enable capturing of the image light waves that are coupled out of the LOE. The eye motion box is a two-dimensional area in which the eye (or image sensor) has a full field of view (FOV) of the image light rays coupled out of the LOE, which correspond to the entire input image, generated by the image projecting optical device, that is coupled into the LOE. In this way, the image sensoracts as the human eye, and the images displayed on the display monitoract as the images that would be seen by the eye of the viewer when using the optical device/system (i.e., the LOEtogether with the image projecting optical device), for example when the viewer wears eyeglasses into which the image projecting optical deviceand the LOEare embedded.

90 80 70 90 80 10 In the other stage, referred to as an orientation alignment stage, the orientation of the image sensoris adjusted so as to align with the orientation of the alignment module, which is linked to the alignment orientation of the LOE. The alignment of the image sensorwith the alignment moduleallows for proper execution of the focusing and alignment stage, in which the components of the image projecting optical deviceare aligned and focused.

1 FIG. 2 FIG. 10 10 12 14 16 18 12 With continued reference to, refer now to, a sectional view illustrating a schematic representation of components of a non-limiting example of the image projecting optical devicefor which the focusing and alignment methods according to embodiments of the present disclosure are to be performed. Generally speaking, the image projecting optical deviceincludes an electronic display source, an illumination module, an illumination prism assembly, and a collimating prism assembly. In a non-limiting implementation, the electronic display sourceis implemented as a liquid crystal on silicon (LCoS) micro-display.

14 12 14 14 The illumination moduleincludes a light source and is configured to transmit light in order to illuminate the image area of the electronic display source. The illumination modulemay be implemented in various ways, and may be a polarized or unpolarized light source. Examples of non-limiting implementations of the light source of the illumination moduleinclude, but are not limited to, a light emitting diode (LED), a light pipe with red-green-blue (RGB) LEDs for color mixing, multiple LEDs that each emit a different color in combination with dichroic mirrors for color mixing, a diode laser, and multiple diode lasers that each emit a different color in combination with dichroic mirrors for color mixing.

2 FIG. 14 16 14 32 20 16 24 16 12 34 20 24 20 22 16 12 12 12 12 16 34 24 16 36 22 18 According to certain non-limiting implementations, such as the implementation illustrated in, the light source of the illumination moduleis a polarized light source, and more specifically is a source that produces s-polarized light waves. The illumination prism assemblyreceives the s-polarized light waves from the illumination modulethrough a light-transmissive surfaceof a first prismof the illumination prism assembly. The received s-polarized light waves are reflected off of a p-polarization transmissive polarizing beamsplitter(which transmits p-polarized light and reflects s-polarized light) and coupled out of the illumination prism assemblytoward the electronic display sourcethrough a light-transmissive surfaceof the first prism. The polarizing beamsplitteris positioned between a slant edge of the first prismand a slant edge of a second prismof the illumination prism assembly. In response to the received illumination of the s-polarized light waves at the image area of the electronic display source, the electronic display sourceis stimulated (i.e., activated) to generate corresponding pixel output in the form of p-polarized light waves emanating from the active pixels of the electronic display source. The p-polarized light waves from the electronic display sourceare coupled into the illumination prism assemblythrough the light-transmissive surfaceand pass through the polarizing beamsplitter. The p-polarized light waves are then coupled out of the illumination prism assemblythrough a light-transmissive surfaceof the second prismand toward the collimating prism assembly.

18 Prior to being coupled into the collimating prism assemblythe light waves may pass through a half-wavelength retardation plate (not shown) to convert the p-polarized light waves to s-polarized light waves.

2 FIG. 18 38 26 18 30 26 28 18 40 42 26 28 18 30 18 40 18 40 30 18 42 18 42 30 18 44 28 18 According to certain non-limiting implementations, such as the implementation illustrated in, the s-polarized light waves are coupled into the collimating prism assemblythrough a light-transmissive surfaceof a first prismof the collimating prism assembly. The coupled-in s-polarized light waves reflect off of a p-polarization transmissive polarizing beamsplitter(which transmits p-polarized light and reflects s-polarized light) that is positioned between a slant edge of the first prismand a slant edge of a second prismof the collimating prism assembly. Although not shown in the drawings, collimating lenses, together with quarter-wavelength retardation plates, may be positioned at opposing light-transmissive surfaces,of the prisms,so as to act to collimate the light waves that ultimately exit the collimating prism assembly. Accordingly, the s-polarized light waves reflect off of the polarizing beamsplitter, are coupled out of the collimating prism assemblythrough the light-transmissive surface, pass through a quarter-wavelength retardation plate, are reflected by a collimating lens, return to pass again through the quarter-wavelength retardation plate (thereby converting the light waves to p-polarized light waves), and re-enter the collimating prism assemblythrough the light-transmissive surface. The p-polarized light waves then pass through the polarizing beamsplitter, are coupled out of the collimating prism assemblythrough the light-transmissive surface, pass through a quarter-wavelength retardation plate, are reflected by a collimating lens, return to pass again through the quarter-wavelength retardation plate (thereby converting the light waves to s-polarized light waves), and re-enter the collimating prism assemblythrough the light-transmissive surface. The now s-polarized light waves are reflected off of the polarizing beamsplitterand are coupled out of the collimating prims assemblythrough a light-transmissive surfaceof the second prism, where they may be coupled into a light-transmissive substrate (e.g., LOE) and ultimately coupled out of the substrate into the eye of a viewer. The coupling-in of light waves may be accomplished via an in-coupling optical surface (e.g., a wedge-shaped prism or an angled reflecting surface) that interfaces the collimating prism assemblyand the LOE input.

16 18 10 Note that for each instance where a particular polarized wave path has been followed in the examples described above, the polarizations are interchangeable. In other words, on altering the orientation of the polarizing beamsplitters, each mention of p-polarized light could be replaced by s-polarized light, and vice versa. As such, the specific use of the particular beamsplitters in the illumination prism assemblyand the collimating prism assemblyin the examples described above are not intended to be limiting, are provided for illustrative purposes in order to better describe the operation of the image projecting optical device.

16 18 34 36 38 44 32 Also note that the light-transmissive surfaces of the prisms of the illumination prism assemblyand the collimating prism assemblydescribed above are generally planar surfaces. As should be apparent, the light-transmissive surfaces,,,are parallel to each other (i.e., are in parallel planes), and are orthogonal to the light-transmissive surface.

10 12 14 16 18 12 10 12 2 FIG. 2 FIG. Although it should be noted that the components of the image projecting optical deviceare not necessarily drawn to scale in, it should be clear fromthat the electronic display source, the illumination module, the illumination prism assembly, and the collimating prism assemblyare out of alignment, causing non-uniformity of the illumination of the electronic display source, and ultimately resulting in a non-uniform and defocused image. Accordingly, focusing and alignment of the major components of the image projecting optical deviceshould be performed to ensure uniformity of the illumination of the electronic display source. The following paragraphs describe the focusing and alignment stage in detail.

3 3 FIGS.A-C 3 FIG.A 10 16 18 46 16 18 46 36 38 36 38 46 46 36 38 46 38 18 Referring now to, focusing and alignment of the components of the image projecting optical deviceaccording to an embodiment of the present disclosure. In, the illumination prism assemblyis deployed in spaced relation relative to the collimating prism assemblyso as to produce and provide a gapbetween the illumination prism assemblyand the collimating prism assembly. The size of the gapis measured as the shortest distance between the light transmissive surfaces,(i.e., the distance along the line that is normal to, and bounded by, the light transmissive surfaces,). In certain embodiments, the gapis a spatial gap implemented as an air gap, while in other embodiments the gapis implemented as a light-transmissive gel deployed between the light-transmissive surfaces,. In yet other embodiments, the gapis implemented as a combination of an air gap and an optical component, for example, a lens that is optically attached to the light-transmissive surfaceof the collimating prism assembly.

46 10 46 14 16 32 61 60 14 10 G 3 FIG.A The initial size of the gapmay vary depending on how the components of the image projecting optical deviceare initially assembled. In typical configurations, the size of the gapis less than 1 millimeter, and in common implementations is approximately 0.5 millimeters. The initial gap size (i.e., width) is denoted as Win. The illumination moduleis mechanically attached to the illumination prismat the light-transmissive surface. The mechanical attachment is made via an alignment mechanism that in certain embodiments is a sub-component of the first sub-assemblyof the mechanical assembly. The alignment mechanism also aligns the illumination modulewith the nominal optical axis of the image projecting optical device.

10 16 18 10 48 48 48 48 32 48 34 3 FIG.A a b a a b In general terms, the optical axis of the image projecting optical deviceis defined in part by the illumination prism assembly, and further in part by the collimating prism assembly. The optical axis of the image projecting optical deviceincludes multiple components, which as illustrated inincludes a first componentof the optical axis and a second componentof the optical axis that is orthogonal to the first component. The first componentis normal to the plane in which the light-transmissive surfacelies, and the second componentis normal to the plane in which the light-transmissive surfacelies.

14 48 12 48 12 14 12 61 14 a b As such, the aforementioned alignment mechanism aligns the illumination modulewith the first componentof the optical axis. The electronic display sourceis aligned, via an alignment mechanism, to the second component. The same alignment mechanism may be used to align the electronic display sourceand the illumination module. Alternatively, the alignment mechanism that aligns the electronic display sourcemay be a sub-component of the first sub-assemblythat is a different sub-component from the alignment mechanism that aligns the illumination module.

12 14 16 14 24 12 12 12 12 12 12 The electronic display sourceand the illumination moduleare aligned with the illumination prism assemblysuch that the light waves emitted by the illumination modulereflect off of the polarizing beamsplitterand arrive at the image area of the electronic display sourceso as to uniformly illuminate the electronic display source. The image area of the electronic display sourceis generally located at a central region of the front portion of the electronic display source(i.e., the center of the LCoS). The alignment of the electronic display sourcemay include moderately tilting or rotating the electronic display sourceabout the X-axis, and/or Y-axis, and/or the Z-axis.

12 34 20 12 34 20 12 34 20 12 61 The electronic display sourcemay be attached (for example via optical cement) to the light-transmissive surfaceof the first prism. Alternatively, the electronic display sourcemay be held mechanically in place next to the light-transmissive surfaceof the first prismwith or without an air gap provided between the electronic display sourceand the light-transmissive surfaceof the first prism. The electronic display sourcemay be help mechanically by a sub-component of the first sub-assembly.

12 14 16 50 61 48 34 20 12 18 12 18 46 16 16 34 36 16 12 34 20 12 16 12 34 b 3 3 FIGS.A-C 3 FIG.A G The electronic display source, the illumination module, and the illumination prism assemblyare displaced (i.e., shifted), in unison as a single unit(i.e., single mechanical unit of the first sub-assembly, demarcated by dashed lines), along a displacement axis that is colinear with the second component, which inis the Z-axis. By equivalence, the displacement occurs along a line that is normal to the light-transmissive surfaceof the first prism. The displacing action effectively moves the electronic display sourcecloser to, or further away from, the collimating prism assembly, thereby adjusting the shortest linear distance between the electronic display sourceand the collimating prism assembly. The linear distance, denoted as D in, is a direct function of the size of the gapintroduced by the deployment of the illumination prism. Specifically, the linear distance D is approximately equal to the sum of the gap width W, the width of the illumination prism assembly(i.e., the shortest distance between the transmissive surfacesand), and the distance between the front panel of the electronic display source and the illumination prism assembly. In embodiments in which the electronic display sourceis cemented to the light-transmissive surfaceof the first prism, the distance between the front panel of the electronic display sourceand the illumination prism assemblyis approximately equal to the layer thickness of the optical cement used to attach the electronic display sourceto the light-transmissive surface.

46 10 10 90 70 12 18 90 1 90 100 12 100 12 100 As the linear distance changes, the size of the gapalso changes, as does the position of the focal plane of the image projecting optical device. As the position of the focal plane changes, the focus of the image, projected by the image projecting optical device, and captured by the image sensorat the output of the LOE, also changes. The displacing action is performed while evaluating an image quality metric, more specifically focus quality, of the captured image, and is performed until a best focus of the captured image is achieved. The image quality metric (i.e., focus quality) of the image may be evaluated, for example, via image processing techniques and methods (performed by a computerized processor, e.g., an image processor), to provide an indication of the distance adjustment (i.e., between the electronic display sourceand the collimating prism assembly) required in order to achieve best focus. The image processing techniques may include, for example, evaluating the modulation transfer function (MTF) at the detector of the image sensor. Alternatively, or in combination with image processing techniques, the focus quality may be visually evaluated by the operator of the environmentby viewing the images, from the image sensor, displayed on the display monitor. Accordingly, as the operator displaces the electronic display sourceso as to adjust the position of the focal plane, the MTF and/or the focus of the image displayed on the display monitorchanges. The displacement of the electronic display sourceis continued until the focal plane is at a position in which the MTF indicates that the image is in focus and/or the operator views a focused image on the display monitor.

3 FIG.B 3 FIG.B 12 14 16 46 50 18 46 G F shows the electronic display source, the illumination module, and the illumination prismsubsequent to the linear displacement to achieve best focus, in which the size of the gapis reduced to a value of less than Was a result of movement of the single unitcloser to the collimating prism assembly. The size of the gap, after achieving best focus, is denoted as Win.

12 18 50 50 38 18 50 34 36 38 50 12 14 16 10 70 70 12 90 70 50 18 12 70 90 70 100 70 3 3 FIGS.A-C Once the distance between the electronic display sourceand the collimating prism assemblyis properly adjusted to ensure best focus, the unitis translationally moved. The unitis translationally moved relative to the light-transmissive surfaceof the collimating prism assembly, and in the plane normal to the displacement axis, which inis the XY-plane. In other words, the unitis translated in a plane parallel to the plane of the light-transmissive surfaces,,. The translational movement of the single unitin the XY-plane is performed without rotation (i.e., without rotation about the displacement axis (i.e., the Z-axis) or the X-axis or the Y-axis). The translation is performed so as to maintain the alignment of the electronic display sourceand the illumination modulewith the illumination prism assembly, and to maintain line of sight (LoS) of the optical system (i.e., between the image projecting optical deviceand the LOE). Within the context of this document, the term “LoS” generally refers to when there is a correspondence between the appropriate individual pixels of the LOEoutput image and the active pixels of the image area of the electronic display source. When LoS is maintained, the image sensor, when positioned in the eye motion box at the eye relief distance, captures the entire image (i.e., full FOV) projected by the LOE. For example, LoS may not be achieved if the unitis translationally offset from the collimating prism assemblyby more than an allowed amount. In such instances, some of the pixels of the source image (i.e., from the electronic display source) may not reach the LOEoutput even when the image sensoris within the eye motion box, the results of which may be manifested in a cutoff image when viewing the LOEoutput image on the display monitor(or equivalently when the image light waves are coupled out of the LOEand into the eye(s) of a viewer).

3 FIG.C 10 70 90 100 70 100 50 12 14 16 12 14 16 12 shows the components of the image projecting optical devicesubsequent to translational movement in the XY-plane. The LoS may be evaluated via image processing techniques (performed by a computerized processor, e.g., an image processor), or may be visually evaluated by the user by viewing the output images from the LOE, captured by the image sensor, displayed on the display monitor. For example, while the LOEoutput image is viewed by the user on the display monitor, the unitmay be translated in the XY-plane until appropriate pixel matching, corresponding to the desired LoS, is achieved. By translating the electronic display source, the illumination module, and the illumination prism assemblytogether as a single unit, uniform illumination of the electronic display sourceby the illumination module(via the illumination prism assembly) is maintained. As such, the center of the electronic display sourceis illuminated throughout the duration of the translational movement in the XY-plane.

50 16 18 36 38 10 After the translational movement of the single unitis complete, the illumination prism assemblyand the collimating prism assemblymay be optically attached to each other at light-transmissive surfaces,, for example via optical cement. As a result, the major components of the image projecting optical deviceare connected to each other, either directly or indirectly.

12 14 16 12 14 16 Although embodiments of the disclosure described thus far have pertained to displacing and translating the electronic display sourcetogether with the illumination moduleand the illumination prism assemblyas a single unit, other embodiments are possible in which the electronic display sourceis displaced independently from the illumination moduleand the illumination prism assembly.

4 4 FIGS.A-B 4 FIG.A 3 3 FIGS.A-C 10 12 16 18 47 47 47 16 18 46 47 12 16 47 12 34 12 34 47 a b a b b b Refer now to, focusing and alignment of the components of the image projecting optical deviceaccording to another embodiment of the present disclosure. In, the electronic display sourceand the illumination prism assemblyare deployed in spaced relation relative to the collimating prism assemblyso as to produce and provide two gaps, namely a first gapand a second gap. The first gapis provided between the illumination prism assemblyand the collimating prism assembly, similar to the gapdescribed in the embodiments with reference to, and should be understood by analogy thereto. The second gapis provided between the electronic display sourceand the illumination prism. The size of the second gapis measured as the shortest distance between the front panel of the electronic display sourceand the light-transmissive surface(i.e., the distance along the line that is normal to, and bounded by, front panel of the electronic display sourceand the light-transmissive surface). In certain embodiments, the second gapis a spatial gap implemented as an air gap.

47 47 10 47 47 a b a b 4 FIG.A G1 G2 The initial sizes of the gaps,may vary depending on how the components of the image projecting optical deviceare initially assembled. Inthe initial size (i.e., width) of the first gapis denoted as Wand the initial size of the second gapis denoted as W.

12 14 16 14 24 12 12 14 16 14 16 32 61 The electronic display sourceand the illumination moduleare aligned with the illumination prism assemblysuch that the light waves emitted by the illumination modulereflect off of the polarizing beamsplitterand arrive at the image area of the electronic display sourceso as to uniformly illuminate the electronic display source. In addition to aligning the illumination modulewith the illumination prism assembly, the illumination moduleis mechanically attached to the illumination prism assemblyat the light-transmissive surfacevia a sub-component of the first sub-assembly.

12 48 34 14 16 12 47 12 16 18 12 18 47 47 16 34 36 b b a b 1 1 G1 G2 4 FIG.A The electronic display sourceis then displaced along the displacement axis (i.e., the axis colinear with the second component, i.e., the axis that is orthogonal to the light-transmissive surface) while the illumination moduleand the illumination prism assemblyare held in place (i.e., are static). The electronic display sourceis displaced to adjust the size of the second gap. The displacing action effectively moves the electronic display sourcecloser to, or further away from, the illumination prism assemblyand the collimating prism assembly, thereby adjusting the shortest linear distance between the electronic display sourceand the collimating prism assembly. The linear distance, denoted as Din, is a direct function of the size of the gaps,. Specifically, the linear distance Dis approximately equal to the sum of the gap widths Wand W, and the width of the illumination prism assembly(i.e., the shortest distance between the transmissive surfacesand.

3 3 FIGS.A-C 4 FIG.B 4 FIG.B 4 FIG.B 12 12 47 12 18 47 47 b a b G2 F2 Similar to as described above with reference to, the electronic display sourceis displaced until best focus is achieved.shows the electronic display sourcesubsequent to the linear displacement to achieve best focus, in which the size of the second gapis reduced to a value of less than Was a result of movement of the electronic display sourcecloser to the collimating prism assembly. As shown in, the size of the first gapremains unchanged. The size of the second gap, after achieving best focus, is denoted as Win.

12 16 34 61 12 14 16 50 3 FIG.C Once best focus is achieved, the electronic display sourceis mechanically attached to the illumination prism assemblyat the light-transmissive surface. The mechanical attachment may be effectuated by one or more sub-components of the first sub-assembly. The electronic display source, the illumination module, and the illumination prism assemblyare then translated, as a single unit (i.e., unit), in the XY-plane, so as to maintain the desired LoS, in a manner similar to as described with reference to.

47 47 12 47 16 14 47 a b b a. In certain embodiments, displacement along the displacement axis may be initiated so as to adjust the size of both gapsand. In such embodiments, the electronic display sourceis displaced to adjust the size of the second gap, while the illumination prism assemblyis displaced along the displacement axis (i.e., the Z-axis), together with the illumination module, to adjust the size of the first gap

3 3 FIGS.A-C 4 4 FIGS.A-B 12 10 12 16 47 12 10 b The embodiments described with reference tohas certain advantages over methods that rely on using gaps close to the electronic display source, for example, in the embodiments described with reference to. One such advantage is that the image projecting optical deviceperforms better optically when there is no gap between the electronic display sourceand the illumination prism assembly(i.e., the second gap). By not having a gap close to the electronic display source, the area close to the focal plane of the image projecting optical deviceremains clean and free from contaminants.

10 61 16 18 36 38 10 14 16 As discussed above, the major components of the image projecting optical deviceare connected to each other, either directly or indirectly. The connections are effectuated by mechanical attachment of the major components via one or more sub-components of the first sub-assembly. In certain embodiments, the mechanical attachment between the illumination prism assemblyand the collimating prism assemblyis effectuated by one or more glass slabs that are cemented to the light-transmissive surfaces,. In other embodiments, a light-transmissive gel is placed between adjacent components of the image projecting optical devicein order to fill unwanted gaps between such components. For example, the gel may be deployed between the illumination moduleand the illumination prism assembly.

5 FIG. 500 500 10 500 1 Attention is now directed towhich shows a flow diagram detailing a processin accordance with the disclosed subject matter. The processincludes steps for focusing and aligning the components of the image projecting optical device. Some of the sub-processes of the processmay be performed manually by an operator of the environmentor may be performed automatically by various mechanical and computerized components, such as processors and the like.

500 502 16 18 46 47 16 18 500 504 14 12 16 14 12 24 12 12 48 16 48 12 14 48 16 48 14 b a a b b The processbegins at block, where the illumination prism assemblyis deployed relative to the collimating prism assemblyso as to produce a gap (i.e., the gap, or the first gap) between the illumination prism assemblyand the collimating prism assembly. The processthen moves to block, where the illumination moduleand the electronic display sourceare aligned with the illumination prism assemblysuch that the light waves emitted by the illumination modulearrive at the image area of the electronic display source, via reflection off of the polarizing beamsplitter, so as to uniformly illuminate the electronic display source. The aligning step includes positioning the electronic display sourcealong the first componentof the optical axis of the illumination prism assemblysuch that the first componentpasses through the center of the electronic display source, and positioning the illumination modulealong the second componentof the optical axis of the illumination prism assemblysuch that the second componentpasses through the center of the illumination module.

504 12 14 16 32 34 504 47 12 16 b In certain embodiments, the aligning performed in blockincludes mechanically attaching the electronic display sourceand the illumination moduleto respective surfaces of the illumination prism assembly(i.e., the orthogonal light-transmissive surfaces,). In other embodiments, the aligning performed in blockincludes producing a gap (i.e., the second gap) between the electronic display sourceand the illumination prism assembly.

500 506 12 12 18 12 10 10 12 14 16 The processthen moves to block, where the electronic display sourceis displaced along the displacement axis (i.e., the Z-axis) to adjust the distance between the electronic display sourceand the collimating prism assemblyin order to achieve best focus. In other words, by displacing the electronic display source, the position of the focal plane of the image projecting optical deviceis adjusted. The focal plane position is adjusted while image quality metrics are evaluated (e.g., MTF) in order to achieve best (i.e., optimal) or near-best focus of the image projected by the image projecting optical device. In certain embodiments, the electronic display sourceis displaced together with the illumination moduleand the illumination prism assembly, such they are displaced in unison, together as a single unit.

12 14 16 12 16 506 In other embodiments, the electronic display sourceis displaced alone while the illumination moduleand the illumination prism assemblyremain static. In such embodiments, the electronic display sourceis mechanically attached to the illumination prism assemblysubsequent to performing the displacing of block.

90 70 As discussed above, the best focus may be determined by evaluating the focus quality of the image (captured by the image sensorat the LOEoutput), via image processing techniques and methods, such as, for example, determining the MTF.

500 508 12 14 16 12 14 16 The processthen moves to block, where the electronic display source, the illumination module, and the illumination prismare translated in unison in the XY-plane in order to maintain the desired LoS. The LoS may be evaluated via image processing techniques. As discussed above, in certain embodiments the translational movement is effectuated by moving the electronic display source, the illumination module, and the illumination prismtogether as a single unit.

10 90 10 90 12 10 As mentioned above, the embodiments directed to methods for performing focusing and alignment of the components of the image projecting optical deviceconstitutes one stage (referred to as the focusing and alignment stage) of a two-stage process. The other stage, referred to as the orientation alignment stage, is performed in order to ensure that the image sensoris properly aligned with the image projecting optical device, so that the images captured by the image sensorduring execution of the method steps of the focusing and alignment stage enable proper alignment of the electronic display sourcewith the remaining components of the image projecting optical device. The following paragraphs describe the orientation alignment stage in detail.

1 FIG. 80 60 62 65 10 70 60 62 61 63 10 70 80 61 63 65 a b Referring again to, the alignment moduleis attached to the mechanical assemblyat a first portionthereof via the third sub-assembly. The image projecting optical deviceand the LOEare mechanically attached to the mechanical assemblyat a second portionthereof via the first sub-assemblyand the second sub-assembly, respectively. The image projecting optical device, the LOE, and the alignment moduleare held in known fixed orientations by the respective sub-assemblies,,.

60 64 62 62 62 62 60 64 a b a b In certain embodiments, the mechanical assemblyincludes a central portionthat provides physical separation between the two portions,. The two portions,may be located at opposite ends of the mechanical assembly, separated by the central portion.

90 60 66 66 90 70 80 The image sensoris attached to the mechanical assemblyvia the sliding arrangement. The sliding arrangementis operative to slide horizontally between two positions so as to alternately align the image sensorwith the LOEand the alignment module.

1 FIG. 6 FIG. 80 80 86 86 80 86 80 80 60 86 60 60 With continued reference to, refer now toa sectional view illustrating a schematic representation of the alignment moduleaccording to an embodiment of the present disclosure. The alignment moduleincludes a test pattern. In a preferred but non-limiting implementation, the test patternis implemented as a generally rectangular slit (i.e., an elongated aperture) formed in a base surface of the alignment module. In other embodiments, the test patterncan be a printed pattern, for example, an elongated rectangular pattern, printed on a base surface of the alignment module. In certain embodiments, the alignment moduleis a component of the mechanical assembly, and therefore the test patternmay be considered as a portion of the mechanical assembly, formed as an aperture or an opening in the mechanical assembly.

86 60 86 86 90 90 90 86 90 80 86 6 FIG. The test patternis positioned at a fixed and known orientation with respect to the mechanical assembly. The orientation of the test patternis defined by one or more orientation parameters. According to embodiments of the present disclosure, the angle of the central axis of the test patternrelative to a reference axis defines the main orientation parameter. In implementations in which the test pattern is implemented as a rectangular slit, the central axis is the long line of reflectional symmetry of the rectangle. The reference axis may be, for example, the axis of horizontal movement of the image sensor, which is the plane of the paper in, or may be the vertical axis that is normal to the axis of horizontal movement of the image sensor. As will described in greater detail below, the image sensoris operative to capture one or more images of the test patternwhen the image sensoris aligned with the alignment modulein order to allow estimation of the orientation parameter (i.e., angle) of the test patternvia image processing algorithms.

6 FIG. 86 86 84 86 82 83 82 84 85 84 86 In certain embodiments, such as the non-limiting embodiment illustrated in, the test patternis illuminated from the back in order to produce a clearer and sharper image of the test pattern. In such embodiments, a diffuseris deployed between the test patternand a light source, implemented, for example, as one or more light emitting diodes (LEDs). Light waves (represented schematically as light rays) emanating from the light sourceare scattered by the diffuser. The scattered light waves (represented schematically as light rays) from the diffuserilluminate the back of the test pattern.

7 FIG.A 66 90 90 92 90 80 86 92 Refer now to, the sliding arrangementin a first position so as to position the image sensorin a first location. When the image sensoris in the first location, the lens(which may include multiple lenses) of the image sensoris aligned with the alignment modulesuch that the test patternis positioned within the field of view of the lens.

8 FIG. 7 FIG.A 8 FIG. 8 FIG. 86 90 90 80 86 86 86 87 86 90 shows a front view of the test pattern, when implemented as a slit, taken from the perspective of the image sensorwhen the image sensoris aligned with the alignment module(). The test patternmay generally be deployed at any known and fixed orientation, including vertically, horizontally, or any angle therebetween. However, orienting the test patternat an angle of approximately 30°, as illustrated in, is advantageous when utilizing certain image processing algorithms (e.g., edge detection algorithms), as such an orientation provides the algorithm with more clearly defined edge regions, thereby more easily accommodating estimation of the orientation of the test pattern. As discussed above, the angle is measured from the central axisof the test patternto the reference axis, which inis the axis of horizontal movement of the image sensor.

7 FIG.A 90 90 90 92 90 86 90 70 90 86 90 86 With continued reference to, the image sensorcaptures one or more images of the test patternwhen image sensoris in the first location. When in the first location, the lensof the image sensoris spaced apart from the test patternby approximately 10-15 centimeters. As mentioned above when discussing the focus and alignment stage, the image sensoris focused to infinity when capturing the image light waves that are coupled out of the LOE. Since it is preferable to keep the image sensorat a fixed focus (i.e., permanently focused to infinity), images of the test patternare preferably captured with the aperture of the image sensorin a decreased aperture state, in order to ensure a sharp image in which the edges of the test patternare distinct and can be more easily identified by image processing algorithms.

90 90 90 86 86 86 90 90 90 90 66 90 92 90 1 90 86 90 The images captured by the image sensor, when the image sensoris in the first location, are analyzed by a computerized processor (e.g., an image processor) linked to the image sensorin order to estimate the orientation (i.e., angle) of the test pattern. The processor compares the estimated orientation of the test patternto the known true orientation of the test pattern. In certain embodiments, the comparison forms a comparison measure, which may be, for example, formed by taking the absolute value of the difference between the estimated orientation and the known orientation. In such embodiments, a determination is made, by the computerized processor, as to whether the estimated orientation is within an allowed tolerance (e.g., +/−τ°). If the estimated orientation is within the allowed tolerance, the image sensoris deemed as being properly aligned. If, however, the estimated orientation is not within the allowed tolerance, the orientation parameter of the image sensoris adjusted. In certain embodiments, the adjustment of the orientation parameter of the image sensoris performed via rotation of the image sensor (via the sub-assembly that attaches the image sensorto the sliding arrangement) about a principle axis of the image sensor, which may be the optical axis of the lens. Subsequent to the orientation parameter adjustment, another image is captured by the image sensor, and the analysis and comparison steps, outlined above, are repeated, until the estimated orientation is within the allowed tolerance. The indication of whether the estimated orientation is within the allowed tolerance may be provided in real-time, so as to allow an operator of the environmentto continuously adjust the orientation parameter of the image sensoruntil a stopping condition is met (i.e., until the estimated orientation of the test patternis within the allowed tolerance). In this way, the orientation parameter (i.e., angle) of the image sensoris adjusted, by the operator, so as to converge to within the allowed tolerance value.

86 86 90 90 90 66 90 92 90 90 90 90 92 8 FIG. In other embodiments, the processor may provide a correction value as output from the comparison between the estimated orientation and known orientation of the test pattern. In such embodiments, if the estimated orientation and known (i.e., true) orientation do not match (within a tolerance value), a correction value is determined by the processor. For example, if the test patternis at a known angle of 30° (as shown in), and the estimated angle is determined to be 35°, the correction value is calculated as 5°. The correction value is applied to the orientation of the image sensorby adjusting the orientation of the image sensorvia rotation of the image sensor (via the sub-assembly that attaches the image sensorto the sliding arrangement) about a principle axis of the image sensor, which may be the optical axis of the lens. The correction value can be calculated as the difference between the estimated angle and the true angle. In such embodiments, the sign of the correction value can be used to indicate the required direction of rotation. In certain embodiments, the image sensoris rotated about a principle axis of the image sensortoward the reference axis (e.g., the axis of horizontal movement of the image sensor) if the correction value is positive, and rotated away from the reference axis if the correction value is negative. Continuing with the above example of a correction value of 5°, the image sensoris rotated about a principle axis of the lensby 5° toward the reference axis

90 80 90 70 70 90 70 66 90 92 90 70 90 70 66 90 7 FIG.B In principle, once the orientation of the image sensoris corrected and properly aligned with the alignment module, the image sensorcan be moved in front of the LOEin order to allow capturing of the image light waves being coupled out of the LOEin accordance with the method steps of the focusing and alignment stage. The movement of the image sensorin front of the LOEis effectuated by moving the sliding arrangementto a second position so as to position the image sensorin a second location in which the lensof the image sensoris aligned with the LOE. Generally speaking, the image sensoris positioned within the eye motion box, at the eye relief distance from the LOE, when in the second location.shows the sliding arrangementin the second position by which the image sensoris positioned at the second location.

86 90 In certain embodiments, the images of the test patterncaptured by the image sensorare grayscale images, for example, 8-bit grayscale images. In such embodiments, each image pixel takes on a value between a minimum pixel value and a maximum pixel value. In certain implementations of 8-bit grayscale images, the minimum pixel value is 0 and the maximum pixel value is 255, while in other implementations the minimum pixel value may be −127 and the maximum pixel value may be 128. The pixel values are representative of the amount of light captured in each specific pixel, with darker pixels corresponding to lower values and brighter pixels corresponding to higher values.

86 90 86 86 As mentioned above, a computerized processor analyzes the images of the test patterncaptured by the image sensor. The image analysis performed by the processor includes the execution of one or more image processing algorithms in order to estimate the angle of the test pattern. The following paragraphs describe an exemplary image processing algorithm according to an embodiment of the present disclosure, which can be used to estimate the angle of the test pattern.

9 FIG. 88 86 86 88 86 88 104 88 104 88 shows an example of a captured imageof the test patternwhen implemented as a slit. Noise and other interfering factors may add variations to the edge and end portions of the test pattern, resulting in the captured imageportraying the test patternas being oblong in shape with various imperfections. For clarity of illustration, superimposed on the imageare a series of horizontal stripswhich slice the imageinto multiple samples. The spacing between the stripsis preferably uniform, and is a function of the sampling rate of the imageexecuted by the exemplary image processing algorithm.

104 88 88 106 88 108 88 9 FIG. For each of the strips, jumps from darker edge pixels to bright edge pixels are identified in order to identify points along the edges of the image. In, the points along the left edge (i.e., side) of the imageare generally indicated as, and the points along the right edge (i.e., side) of the imageare generally indicated as. For clarity of illustration, only some of the points on the edges of the imageare labeled.

The jumps may be identified using various mathematical methods. For example, the first derivative of the light intensity function of the image can be evaluated to determine an image gradient. The image gradient can then be analyzed, specifically by looking for high values in the image gradient which correspond to jumps. Edge detection algorithms may also be applied in order to identify the jumps, with varying degrees of accuracy.

106 108 Line fitting techniques are used to construct two separate lines, one line that fits the points, and a second line that fits the points. Examples of such techniques, include, but are not limited to, regression techniques, for example, simple linear regression and total least squares, which includes orthogonal regression and Deming regression.

10 FIG. 107 106 109 108 107 109 90 107 109 86 shows the results of the line fitting, in which a first linefits the points, and a second linefits the points. The angles of the first lineand the second line, measured relative to the reference axis (e.g., axis of horizontal movement of the image sensor), are calculated. The angle of the first lineis denoted by α, and the angle of the second lineis denoted by β. The angles α and β are averaged together to produce the estimated angle of the test pattern.

86 86 86 86 86 Although the exemplary interpolation-based image processing algorithm has been described above within the context of the test patternimplemented as a rectangular slit, the same or similar interpolation-based image processing algorithm may be used in embodiments in which the test patternis implemented as a non-rectangular slit. Regardless of the shape of the test pattern, the same basic principles of line fitting edges of the test patternmay apply. The angles of the fit lines relative to the reference axis can be calculated, and the calculated angles for each of the fit lines of the test patterncan be combined, according to mathematical principles (e.g., statistical principles, geometric principles, etc.).

11 FIG. 1100 1100 90 1100 1 Attention is now directed towhich shows a flow diagram detailing a processin accordance with the disclosed subject matter. The processincludes steps for aligning the image sensor. Some of the sub-processes of the processmay be performed manually by an operator of the environmentor may be performed automatically by various mechanical and computerized components, such as processors and the like.

1100 1102 10 70 61 63 1100 1104 90 80 90 66 The processbegins at block, where the image projecting optical deviceand the LOEare mechanically attached to the mechanical assembly, at known and fixed orientations, via the respective sub-assemblies,. The processthen moves to block, where the image sensoris moved to the first location, i.e., into alignment with the alignment module. As discussed above, the movement of the image sensoris facilitated by movement of the sliding arrangement.

1100 1106 90 86 100 1 1108 86 86 100 1 86 86 The processthen moves to block, where the image sensorcaptures one or more images of the test pattern. The image of the test patternmay be displayed on the display monitorfor viewing by the operator of the environment. The process then moves to block, where each captured image of the test patternis analyzed, by a processor (e.g., an image processor), in order to determine an estimated orientation (i.e., angle) of the test pattern. The estimated angle may be displayed on the display monitorfor viewing by the operator of the environment. In embodiments in which multiple images of the test patternare captured, the processor may process each of the images separately in order to produce multiple estimates of the orientation of the test pattern. The multiple estimates may then be combined into a single estimate via averaging or other statistical methods known in the art. Alternatively, the processor may co-process the images together to form a single orientation estimate.

86 As discussed above, various image processing techniques may be used to estimate the orientation of the test pattern. The image processing techniques include, but are not limited to, line fitting algorithms, edge detection algorithms, and any combination thereof.

1108 1100 1110 86 86 1100 1112 1110 1112 1100 1116 1112 90 70 66 1100 1118 90 70 1118 500 From block, the processmoves to block, where the known orientation of the test patternand the estimated orientation of the test pattern(based on the captured image) are compared to form a comparison measure. The comparison measure may be formed, for example, by taking the absolute value of the difference between the estimated orientation and the known orientation. The processthen moves to block, where a determination is made, based on the comparison measure output from block, as to whether the estimated orientation is within an allowed tolerance. The determination in blockmay be made, for example, by evaluating the comparison measure against a threshold criterion. For example, the absolute value of the difference between the estimated orientation and the known orientation may be evaluated against an allowed tolerance value, to determine if the difference is greater than the allowed tolerance value or less than (or equal to) the allowed tolerance value. In principle, the allowed tolerance value may be on the order of several hundredths of a degree and up to one or two tenths of a degree. If the estimated orientation is within the allowed tolerance, the processmoves to blockfrom block, where the image sensor, now deemed as properly aligned, is moved to the second location, i.e., into alignment with the LOE. As discussed above, the movement to the second location is facilitated by movement of the sliding arrangement. The processthen moves to block, where the image sensorcaptures the image light waves that are coupled out of the LOE. The execution of blockmay be performed as one or more of the steps performed in the process.

1100 1114 1112 90 90 92 90 1114 1100 1106 86 90 1106 1114 1100 1116 1112 If, however, the estimated orientation is not within the allowed tolerance (e.g., not within 0.1° of the known orientation), the processmoves to blockfrom block, where an orientation parameter of the image sensor, i.e., the angle about a principle axis of the image sensor(e.g., the optical axis of the lens), is adjusted (i.e., the image sensoris rotated about its principle axis). From block, the processthen returns to block, where a new image of the test patternis captured by the image sensor. The blocks-are repeated as necessary until the estimated orientation is within the allowed tolerance, where the processmoves to blockfrom block, as described above.

1100 1 90 1106 1114 1 100 The iterative nature of the processallows an operator of the environmentto align the image sensorin a relatively short period of time. In certain embodiments, the image capture, analysis, comparison, determination, and adjustment executed in blocks-are performed such that the processor is able to provide the operator with a continuous or near-continuous indication of whether the estimated orientation is within the allowed tolerance. The indication of whether the estimated orientation is within the allowed tolerance may be displayed visually to the operator of the environment, for example via the display monitor.

1 1100 90 10 70 70 90 70 Note that the allowed tolerance may be a pre-determined value that is programmed into a memory of a computer or computing device (e.g., the processor or other processing device linked to the processor) that is operated by operator of the environment. In certain embodiments, various tests and experiments may be performed prior to executing the method steps of the process. Such test and experiments may use the image sensor, the image projecting optical device, and the LOE, in order to evaluate system performance according to performance metrics (e.g., quality and accuracy of the image coupled out of the LOE) as a function of the orientation error between the image sensorand the LOE. The allowed tolerance value may then be determined and programmed based on the performance metrics that meet system performance requirements according to system level specifications. For example, the performance metrics may indicate that the overall system meets performance requirements when the tolerance value is 0.10°, but fails to meet such requirements when the tolerance value is 0.15°.

1100 1106 1114 1110 90 90 1106 1108 1114 Although the embodiments of the processdescribed above have pertained to image capture, analysis, comparison, determination, and adjustment, as executed in blocks-, being performed to allow a processor to provide a continuous or near-continuous indication of whether the estimated orientation is within the allowed tolerance, other embodiments are possible in which the processor provides discrete correction values in response to the comparison performed in block. For example, the comparison output may be treated as a correction value, to be applied to the orientation parameter of the image sensor. In such embodiments, the orientation parameter of the image sensoris adjusted based on the determined correction value. In such embodiments, the steps of image capture, comparison, and adjustment, as executed in blocks,, and, respectively, may be repeated until the estimated orientation is within a predefined allowed tolerance value (e.g., +/−τ°where τ may be approximately 0.10°).

1104 1114 500 90 1116 1118 10 70 It is further noted that blocks-may be executed subsequent to the execution of one or more of the steps described in the process, in order to check/correct the alignment of the image sensor. Furthermore, subsequent executing blocks-, the image projecting optical deviceand the LOEmay be swapped out for a new image projecting optical device and LOE, and the alignment procedure may be continued to ensure proper alignment of the new image projecting optical device and LOE.

60 1102 1104 1114 1116 1118 Alternatively, two sets of image projecting optical devices and LOEs, such as used in stereo vision systems, may be deployed and mechanically attached to the mechanical assembly(i.e., blockmay be performed twice, once for each LOE/image projecting optical device pair). Subsequent to performing blocks-, blocks-may be performed twice, once for each LOE/image projecting optical device pair.

80 Although the embodiments of the present disclosure as described thus far have pertained to utilizing a single image sensor, moveable between two positions, to alternately capture images of the alignment moduleand from the LOE output, other embodiments are possible in which more than one image sensor is deployed to capture images. In such embodiments, for example, two image sensors may be used, with the first image sensor operating at a lower resolution than the second image sensor. Such embodiments may be used to advantage in situations in which the focusing and alignment stage is carried out as a coarse-fine process, in which coarse adjustments are made based on images captured by the lower resolution image sensor, and fine adjustments are made based on images captured by higher resolution image sensor.

500 1100 500 1100 In discussing the execution of the steps of the processesand, references were made to the movement of various mechanical and optical components, as well as the execution of image processing functions. The following paragraphs describe non-limiting examples of instrumentation (i.e., components) and techniques used to perform the method steps associated with the processesand.

500 1100 506 508 500 1108 1100 1100 1110 1112 As discussed in detail above, several of the method steps associated with the processesand, in particular blocksandof the process, and blockof the process, are performed by the execution of various image processing techniques. The image processing techniques may be executed by a computerized processor, which may be part of a processing system. In addition, several of the method steps associated with the process, in particular blocksand, involve performing logic operations including comparisons and determining whether outputs from the comparisons satisfy threshold criteria (i.e., whether the absolute difference between the estimated orientation and the known orientation is greater than or less than an allowed tolerance value). Such logic operations, in the form of comparisons and evaluations against threshold criteria, are preferably performed by computerized processors, which in certain embodiments is the same processor that performs the image processing techniques.

12 FIG. 110 110 90 100 110 90 100 shows a block diagram of an example architecture of such a processing system, generally designatedthat includes at least one computerized processor. The processing systemis linked to the image sensorand the display monitor, such that processing systemcan receive image data from the image sensor, and provide processed output to the display monitorfor display.

110 112 114 112 112 114 112 112 112 The processing systemincludes at least one processorcoupled to a storage modulesuch as a memory or the like. The processorcan be implemented as any number of computerized processors, including, but not limited to, a microprocessor, an ASIC, and a DSP. In certain non-limiting implementations, the processoris advantageously implemented as an image processor. All of such processors include, or may be in communication with non-transitory computer readable media, such as, for example, the storage module. Such non-transitory computer readable media store program code or instructions sets that, when executed by the processor, cause the processorto perform actions. Types of non-transitory computer readable media include, but are not limited to, electronic, optical, magnetic, or other storage or transmission devices capable of providing a processor, such as the processor, with computer readable instructions.

112 506 508 500 1108 1100 1110 1112 1100 114 112 110 In certain embodiments, the processoris configured to perform image processing functions, in accordance with blocksandof the process, and blockof the process, and is further configured to perform other various logic functions, for example in accordance with blocksandof the process. In embodiments in which determinations are made as to whether the estimated orientation is within an allowed tolerance, the storage modulemay be configured to store the allowed tolerance value (or values). Alternatively, the allowed tolerance value may be stored in a volatile or non-volatile memory of the processor. In other embodiments, the various aforementioned image processing and logic functions are performed by separate processors, which are part of the same processing system, or may be part of separate similar processing systems that are linked to each other.

90 112 In embodiments in which differences between the estimated orientation and known orientation are used to determine a correction value to be applied to the orientation parameter of the image sensor, the processormay be configured to determine the correction value.

500 1100 506 508 500 1104 1114 1116 1100 60 60 500 1100 13 14 FIGS.and As further discussed above, the image processing steps are executed in conjunction with movement of various mechanical and optical components. Such movement is outlined in the method steps associated with the processesand, in particular blocks-of the process, and blocks,andof the process. As discussed, the movement of the aforementioned components is enabled by various sub-assemblies of the mechanical assembly. The following paragraphs, with reference to, describe a more detailed non-limiting schematic representation of the mechanical assemblyaccording to an embodiment of the present disclosure, that can be used when performing the steps of the processesand.

13 FIG. 60 602 604 606 608 604 604 606 610 606 610 602 608 612 66 66 602 604 606 66 614 612 612 90 615 612 614 90 As shown in, the mechanical assemblyincludes a basethat is generally planar and extends between to ends, namely a first endand a second end. A sliding railis mechanically attached, via screws or the like, to the baseand extends between the two ends,. A standextends upward from the base near the second end. The standis fixedly mounted to the basevia mechanical fasteners, such as screws or bolts and the like. The sliding railand a baseof the sliding arrangementare correspondingly configured, so as to allow the sliding arrangementto move laterally across the basebetween the two ends,. The sliding arrangementhas a standthat extends upward from the base, and that is mechanically attached to the basevia mechanical fasteners, such as screws or bolts and the like. The image sensoris mechanically coupled to a top portion(i.e., distal portion from the base) of the standvia a mechanical sub-assembly that allows adjustment of the orientation of the image sensor.

608 70 80 86 66 70 80 66 66 1 66 66 In certain embodiments, stoppers may be deployed at different positions along the sliding rail, for example at or near the horizontal position of the LOEand the alignment module(i.e., the test pattern). In this way, the sliding arrangementmay move between two resting positions, so as to alternately align with the LOEand the alignment module. In certain embodiments, the movement of the sliding arrangementis manually induced (i.e., hand-operated by a user of the optical test bench). In other embodiments, the sliding arrangementis electro-mechanically operated, and movement thereof is enabled by a driving arrangement (e.g., actuator with mechanical linkage) coupled to a computer or computing device that allows the user of the optical test bench (i.e., the environment) to actuate movement of the sliding arrangementbetween the resting positions via a user interface or the like implemented on the computer or computing device. In still yet other embodiments, the movement of the sliding arrangementis manually induced and aided by an electro-mechanical driving arrangement.

13 FIG. 616 610 616 70 18 63 70 18 610 60 18 10 18 70 616 60 63 610 63 70 60 also shows a memberdeployed relative to the stand. The memberis a schematic representation of the LOE, the collimating prism assembly, and the second sub-assemblywhich fixedly mounts the LOEand the collimating prism assemblyto the standof the mechanical assemblyin a fixed and known orientation. Although the collimating prism assemblymay be considered as one of the components of the image projecting optical device, the collimating prism assemblymay be attached to the LOEvia an optical attachment (e.g. cement) or a mechanical attachment (e.g., a bracket arrangement or the like). The mounting of the memberto the mechanical assemblyis made via mechanical attachment of the second sub-assemblyto an upper portion of the stand. The second sub-assemblymay include one or more brackets and/or one or more stoppers arranged to hold the LOEin a known and fixed position and orientation relative to the mechanical assembly.

50 616 50 12 14 16 50 61 61 618 620 50 618 620 50 622 624 50 12 14 16 12 14 FIG. 14 FIG. The single unitis positioned behind the member. The single unitis a mechanical body that holds the electronic display source, the illumination module, and the illumination prism assembly.shows a more detailed illustration of the single unit, as well as the first sub-assembly, according to a non-limiting example construction. In the non-limiting construction, the first sub-assemblyis implemented as a double clamping arrangement, that includes an upper clamping memberand a lower clamping member, configured to hold the single unit. The clamping members,respectively hold the top and bottom portions of the single unit, and are connected together by a central pinand an end joint. The single unitmay be formed as a closed or semi-closed box-like structure having the electronic display source, the illumination module, and the illumination prism assemblyhoused therein. In the non-limiting construction shown in, the electronic display sourceis coupled to the housing via a base plate and mechanical fasteners (e.g., screws).

624 610 61 616 50 500 Although not shown in the drawings, the jointis mechanically attached to the standvia a mechanical linkage. An arrangement of adjustment mechanisms (e.g., knobs, dials, etc.) are coupled to the mechanical linkage to facilitate the adjustable positioning of the first sub-assemblyrelative to the member, so as to allow for the displacing and translational moving of the single unitin accordance with the process.

506 508 61 50 50 With respect to the displacement described in block, and the translational movement described in block, the displacing and translational actions may be performed by applying force to one or more sub-components of the first sub-assembly. In certain embodiments, the displacing and translational actions are induced manually (i.e., hand-operated) by an operator/user operating one or more of the adjustment mechanisms coupled to the mechanical linkage. Such manual operations may include, for example, hand operation of the one or more adjustment mechanisms, which may include, for example, turning of knobs or dials. For example, turning one set of knobs or dials may displace the single unitby an incremental amount in proportion to the amount and direction of turn of the knob/dial. Similarly, turning another set of knobs or dials may translate the single unitan incremental amount in proportion to the amount and direction of turn of the knob/dial.

It is noted that in principle the displacement and translational amounts are typically on the order of several micrometers (e.g., tens of micrometers and possibly up to a few hundred micrometers), and many types of equipment used in optical laboratory test benches provide mechanical assemblies and instruments capable of accommodating small adjustment amounts based on hand-operation of the such instruments.

50 616 16 18 36 38 16 18 50 500 16 18 16 18 In practice, one or more slabs of glass may be placed between the single unitand the memberto provide an interface region between the illumination prism assemblyand the collimating prism assembly. As an example, the slabs may be positioned between the adjacent light-transmissive surfacesandof the prism assemblies,. After the single unitis displaced and translationally moved (per the method steps of the process), optical cement may be applied between the slabs and the adjacent surfaces of the prism assemblies,to form an optical attachment between the prism assemblies,.

13 FIG. 13 FIG. 13 FIG. 80 610 65 65 610 616 60 65 628 626 610 628 610 630 628 86 630 82 84 630 628 Returning to, the alignment moduleis mechanically coupled to a side portion of the standvia the third sub-assembly. The third sub-assemblyis attached to the side portion of the standnear the member. In the schematic representation of the mechanical assemblyillustrated in, the third sub-assemblyincludes an extending armthat is mechanically attached, at a first end, to the side portion of the stand. The mechanical attachment of the extending armto the standis made via mechanical fasteners, such as screws or the like. A base plateis deployed at a second end of the extending arm. The test patternis arranged on the base plate. Although not shown in, the light sourceand the diffuserare attached to the back side of the base plate(i.e., behind the test pattern).

70 80 60 70 60 90 90 70 70 80 60 60 80 70 90 80 90 70 It is noted that the attachment of the LOEand the alignment moduleto the mechanical assemblyis performed prior to the execution of the steps of the alignment methodologies described in the present disclosure. The LOEis attached to the mechanical assemblyin a fixed orientation, such that, when the image sensoris positioned in the eye motion box at the eye relief distance, image capture (by the image sensor) of the entire image (i.e., full FOV) projected by the LOEis enabled. The attachment of the LOEand the alignment moduleto the mechanical assemblyis made using various types of optical test equipment known in the art, including, for example, autocollimators, which facilitate attachment of the aforesaid components to the mechanical assemblyin known and fixed orientations with relatively high accuracy levels. In this way, a linkage is established between the orientation of the alignment moduleand the orientation of the LOE, such that correction of the alignment of the image sensorrelative to the alignment moduleensures proper alignment of the image sensorrelative to the LOEas well.

50 60 Although the displacing and translational actions of the single unit, as described above, may be induced via hand-operation of one or more adjustment mechanisms of the mechanical assembly, other embodiments are possible, in which such adjustment mechanisms are operated by an electro-mechanical control system.

15 FIG. 120 120 110 122 124 122 122 122 122 is a block diagram of an example architecture of such an electro-mechanical control system, generally designated. The electro-mechanical control systemis linked to the processing systemand includes a controllerand an actuator. The controllercan be implemented as any number of computerized processors, including, but not limited to, a microcontroller, a microprocessor, an ASIC, and a DSP. All of such processors include, or may be in communication with non-transitory computer readable media that stores program code or instructions sets that, when executed by the controller, cause the controllerto perform actions. Types of non-transitory computer readable media include, but are not limited to, electronic, optical, magnetic, or other storage or transmission devices capable of providing a processor, such as the controller, with computer readable instructions.

124 61 122 122 110 124 The actuatormay be a mechanical actuator, for example a stepper motor, that causes the displacing and translational actions by applying force to one or more sub-components of the first sub-assemblyin response to controlled input from the controller. The controllermay receive image quality metrics, such as the focus quality and LoS evaluation, as input from the processing system, so as to provide feedback control to the actuatorto adjust the adjustment mechanisms based on the focus quality and LoS evaluation.

124 90 124 90 66 124 122 122 110 1112 110 120 120 90 86 120 90 110 86 120 110 In certain embodiments, the actuatormay also control the adjustment of the orientation parameter of the image sensor. In such embodiments, the actuatorcauses rotational adjustment by applying force to the sub-assembly that attaches the image sensorto the sliding arrangement. The actuatorinduces such rotational adjustment in response to controlled input received from the controller. The controlled input is provided by the controllerin response to output from the processing systemindicative of whether the estimated orientation is within the allowed tolerance, in accordance with block. The processing systemand the electro-mechanical control systemmay together form a closed loop system that enables convergence to within the allowed tolerance value. In such a closed loop system, the electro-mechanical control systemactuates the image sensorto capture images of the test pattern. The electro-mechanical control systemthen adjusts the orientation parameter of the image sensorin response to input from the processing systemderived from image analysis performed on the captured images of the test pattern. The actuation, adjustment, and image analysis functions, performed by the electro-mechanical control systemand the processing system, are repeated until the estimated orientation (from the image analysis) is within the allowed tolerance value.

124 66 124 122 66 122 122 66 66 122 In certain embodiments, the actuatormay also control the movement of the sliding arrangement. In such embodiments, the actuatorreceives controlled input from the controllerto slide the sliding arrangementbetween the first and second positions. In such embodiments, the controlleris preferably linked to a computer or computing device having a user interface implemented thereon, to allow the operator to provide input commands to the controllerin order to initiate controlled movement of the sliding arrangement. Alternatively, the motion of the sliding arrangementmay be fully automated by the controller.

Note that in certain embodiments, the image processing and control functionality may be implemented by a single processing-control subsystem having one or more processors.

90 70 70 10 70 70 70 As discussed above, when performing the method steps of the alignment methods of embodiments of the present disclosure, the image sensorcaptures image light waves that are coupled out of the LOE. The LOEfunctions as an optical waveguide that guides light waves from an input optical surface to an output optical surface. In certain non-limiting implementations, the image light waves from the image projecting optical deviceare coupled into the LOEand are guided through the LOE, by total internal reflection. The guided light waves are then coupled out of the LOEas image light waves by one or more partially reflecting surfaces. When in use by the end-user (i.e., subsequent to final assembly in eyeglasses or the like), the coupled-out light waves are projected into an eye (or eyes) of the user (i.e., viewer).

16 FIG. 130 132 134 136 138 10 136 140 130 142 140 132 134 130 140 132 134 130 142 144 146 148 144 140 130 146 148 142 130 142 130 138 142 146 146 138 138 144 130 140 138 130 132 134 130 150 130 130 edge illustrates an example of an implementation of an LOE. The LOE is formed of a light waves-transmitting planar substratethat includes a major lower surfaceand a major upper surfacethat are parallel to each other. A coupling-in optical elementis illuminated by collimated light waves (represented by optical ray) from the image projecting optical device. The coupling-in optical elementincludes a slanted edgeof the substrateand a prism. The edgeis oriented at an oblique angle with respect to the major lower and upper surfaces,of the substrate, wherein αis the angle between the edgeand the normal to the major lower and upper surfaces,of the substrate. The prismincludes three major surfaces,,, with the surfacebeing located next to the edgeof the substrate, and surfacesandbeing polished surfaces. In certain embodiments, the refractive index of the prismis similar to the refractive index of the substrate, while in other embodiments the prismand the substratehave different refractive indices. The optical rayenters the prismthrough the surface. The surfaceis preferably oriented normally to the central light wave of the incoming ray (i.e., the optical ray). The optical raythen passes through the surfaceto enter the substratethrough the edge, whereby the optical rayis trapped inside the planar substrateof the LOE by total internal reflection. After several reflections of the major lower and upper surfaces,of the substrate, the trapped waves reach a coupling-out optical arrangement, implemented for example, as an array of selective partially reflecting surfaces, which couple the light waves out of the substrateout of the substrate.

16 FIG. 70 150 130 90 When the LOE ofis used as the LOEwhen performing the method steps of the alignment methods of embodiments of the present disclosure, the coupling-out optical arrangementcouples the light waves out of the substrateso that the coupled-out light waves may be captured by the image sensor.

16 FIG. 140 132 130 136 132 134 130 132 130 134 132 Note that althoughdepicts the input surface of the LOE (i.e., the surface through which the input light waves enter the LOE) is on the slanted edgeand the output surface of the LOE (i.e., the surface through which the trapped waves exit the LOE) is on the lower major surface, other configurations are envisioned. In one such configuration, the input and output surfaces could be located on the same side of the substrate. In such a configuration, the coupling-in optical elementmay be realized by a reflecting surface that is oriented at an oblique angle with respect to the major lower and upper surfaces,of the substrate, such that the input surface of the LOE is on the major lower surfaceand the coupling-in reflecting surface reflects the incident light waves such that the light is trapped inside the substrateby total internal reflection. Still yet other configurations are envisioned in which the input surface is on the major upper surfaceand the output surface is on the major lower surface.

16 FIG. 150 130 154 152 152 156 70 158 158 156 152 70 at When the LOE ofis in use by the end-user, the coupled-out light waves are projected into an eye (or eyes) of the user (i.e., viewer). Specifically, the coupling-out optical arrangementcouples the light waves out of the substrateinto a pupilof an eyeof the viewer, which form an image viewed by the viewer. The eyeis positioned at the eye relief distancefrom the LOE, and within the eye motion box. As discussed above, the eye motion boxis a two-dimensional area at the eye relief distancewhich the eyecaptures the entire image (i.e., full FOV) projected by the LOE.

70 10 10 70 132 134 130 70 10 152 70 10 10 130 In certain embodiments, the LOE, together with the image projecting optical device, provides an augmented reality environment for the user in which the images from the image projecting optical devicethat are coupled out of the LOEcan be overlaid on the real-world scene. In such embodiments, images from the real-world scene pass directly through the major lower and upper surfaces,of the substrateinto the eye of the viewer, while the LOEsimultaneously couples images (i.e., virtual images) from the image projecting optical deviceinto the eye. In other embodiments, the LOE, together with the image projecting optical device, provides a virtual reality environment for the user in which only the virtual images from the image projecting optical deviceare viewed by the user. In such embodiments, external real-world scene images are not transmitted though the substrate.

10 The LOE can be used as part of a mono-ocular optical system, in which images are projected into a single eye of the viewer. Alternatively, it may be desirable to project images into both eyes of the viewer, such as in head-up display (HUD) applications and stereo vision systems. In such alternatives, two optical systems can be used, with each optical system having an image projecting optical device and an LOE deployed for projecting images into a different eye of the viewer. For example, a HUD employing two optical systems may be installed in front of a car driver, for example integrated into the dashboard of a vehicle, so as to provide assistance in driving navigation or to project thermal images into the eyes of the driver in low-visibility conditions. In such embodiments, a thermal camera may be deployed to capture thermal images of the real-world scene. The thermal images may then be provided to the image projecting optical deviceto enable coupling-in of light waves corresponding to the thermal images into the LOE.

The alignment methods of the embodiments of the present disclosure can be used to advantage in dual-optical systems (i.e., two LOE/image projecting optical device pairs), such as in HUD applications and stereo vision systems, which require proper alignment of the components of each LOE/image projecting optical device pair, as well as alignment of the two optical systems with each other, to ensure correct stereo images.

70 150 150 132 130 136 140 142 132 134 16 FIG. Although the alignment methods of the embodiments of the present disclosure have been described within the context of an optical waveguide implemented as an LOE, for example the LOEof, the alignment methods of the present disclosure may be applicable to other types of optical waveguide technologies, including waveguides that rely on diffractive techniques to couple light waves into and/or out of a light waves-transmitting substrate. For example, instead of implementing the coupling-out optical arrangementas an array of selectively partially reflecting surfaces, the coupling-out optical arrangementcan be implemented as one or more diffractive elements that extends along portions of the major lower surfaceof the substrate. As a further example, instead of the implementing the coupling-in optical elementas a slanted edgetogether with a prism, or as a reflecting surface oriented at an oblique angle, the coupling-in optical element can be implemented as a diffractive element that extends along a portion of the either the major lower surfaceor the major upper surface.

The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

As used herein, the singular form, “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.